render directly to Texture rather than PlatformView (Android only)

lib/filament_widget.dart

@@ -0,0 +1,88 @@
+import 'package:flutter/rendering.dart';
+import 'package:flutter/widgets.dart';
+import 'filament_controller.dart';
+
+
+typedef ResizeCallback = void Function(Size oldSize, Size newSize);
+
+class ResizeObserver extends SingleChildRenderObjectWidget {
+  final ResizeCallback onResized;
+
+  const ResizeObserver({
+    Key? key,
+    required this.onResized,
+    Widget? child,
+  }) : super(
+          key: key,
+          child: child,
+        );
+
+  @override
+  RenderObject createRenderObject(BuildContext context) =>
+      _RenderResizeObserver(onLayoutChangedCallback: onResized);
+}
+
+class _RenderResizeObserver extends RenderProxyBox {
+  final ResizeCallback onLayoutChangedCallback;
+
+  _RenderResizeObserver({
+    RenderBox? child,
+    required this.onLayoutChangedCallback,
+  }) : super(child);
+
+  late var _oldSize = size;
+
+  @override
+  void performLayout() {
+    super.performLayout();
+    if (size != _oldSize) {
+      onLayoutChangedCallback(_oldSize, size);
+      _oldSize = size;
+    }
+  }
+}
+
+class FilamentWidget extends StatefulWidget {
+
+  final FilamentController controller;
+
+  const FilamentWidget({Key? key, required this.controller}) : super(key: key);
+
+  @override
+  _FilamentWidgetState createState() => _FilamentWidgetState();
+}
+
+class _FilamentWidgetState extends State<FilamentWidget> {
+
+  bool _ready = false;
+
+  @override
+  void initState() {
+    WidgetsBinding.instance.addPostFrameCallback((timeStamp) async {
+      var size = ((context.findRenderObject()) as RenderBox).size;
+      print("Requesting texture creation for Filament of size $size");
+      await widget.controller.initialize(size.width.toInt(), size.height.toInt());
+      print("Filament texture available");
+      setState(() {
+        _ready = true;
+      });
+    });
+    
+    super.initState();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    if(!_ready) {
+      return Container();
+    }
+    return ResizeObserver(
+      onResized: (Size oldSize, Size newSize) async {
+        await widget.controller.resize(newSize.width.toInt(), newSize.height.toInt());
+      },
+      child:Texture(
+      textureId: widget.controller.textureId,
+      filterQuality: FilterQuality.none,
+    ));
+  }
+}